1. Field
Embodiments of the invention relate to the field of networking; and more specifically to providing inter-chassis redundancy.
2. Background Information
FIG. 1 is a block diagram of a known 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) architecture cellular network 100. User equipment (UE) 101 (e.g., mobile phones, laptops, Machine to machine (M2M) devices, and other wireless devices) may establish wireless connections 102 with the LTE network through an eNodeB 103. The eNodeB represents the LTE network base station that serves as an access point for the user equipment connectivity to the LTE network. Generally there will be a number of geographically distributed base stations that are used by the user equipment to access the network.
User data (e.g., IP packets) sent from and/or delivered to the user equipment (UE) may be processed by a Serving Gateway (S-GW) 104 and a Packet Data Network Gateway (PDN-GW) 105. The S-GW is coupled or in communication with the eNodeB by a user plane interface (S1U). This interface may handle the per-bearer user plane tunneling and inter-eNodeB path switching during handover. The S-GWs may receive user data over the S1U interfaces and may buffer downlink IP packets destined for UE that happen to be in idle mode. The S-GWs is coupled or in communication with a Mobility Management Entity (MME) 106 by an S11 interface. The MME represents a control-node for the LTE access-network and generally provides subscriber and session management. The S-GW is coupled or in communication with the PDN-GW by an S5 interface. The S5 interface may provide user plane tunneling and tunnel management between the S-GW and the PDN-GW and may be used for S-GW relocation due to user equipment mobility. The PDN-GW may include logic for IP address allocation, charging, packet filtering, policy-based control of flows, etc. The PDN-GW 105 may also serve as a gateway towards external IP networks (e.g., the Internet) 107. For example, the PDN-GW may be coupled with one or more edge network elements that provide access to the Internet.
The S-GW, PDN-GW, and MME are subcomponents of the Evolved Packet Core (EPC) or core network architecture 108 of LTE. The S-GW, PDN-GW, and MME are logically separate entities according to LTE, although they may be physically deployed on either one or more physical network elements and/or chassis. For example, a combined gateway (C-GW) may combine the S-GW and PDN-GW logical entities within a single network element or chassis. The network may include other network elements (not shown), such as, for example, one or more routers and/or switches between the eNodeB and the S-GW, between the S-GW and the PDN-GW, and/or between the PDN-GW and the Internet.
FIG. 2 is a block diagram of a known approach for transporting Layer 2 data 210 over an LTE network 200. The LTE network is an all-IP network operating at Layer 3 of the OSI model. Currently, the LTE network does not provide support for transporting the Layer 2 data 212, or data link layer data, as such. A Layer 2 device 209 is to transmit Layer 2 data toward the LTE network. By way of example, the Layer 2 data may represent an Ethernet bit stream (e.g., Ethernet frames). The LTE network having a PDN-GW 205 and a S-GW 204 receives the Layer 2 data. A Layer 3 encapsulation module 211 of the LTE network, often deployed in a PDN-GW 205, or alternatively employed in a combined gateway having the PDN-GW and the S-GW 204, is operable is to encapsulate the Layer 2 data within a Layer 3 format. The Layer 3 encapsulated Layer 2 data 212 is then transmitted toward user equipment (UE) 201. By way of example, such an approach may allow fixed Layer 2 device to transmit Layer 2 data to cellular phones or other user equipment leveraging the LTE network.
FIG. 3 is a block diagram of a known encapsulation approach for transporting Layer 2 data over an LTE network. A Layer 2 device 309 provides Ethernet data having Service Labels (e.g., an S-Vlan (S) and a C-Vlan (C)). A soft-Generic Routing Encapsulation (GRE) device (e.g., a cross-connect device) 313 may encapsulate the Ethernet data with inner IP, GRE, and Multiprotocol Label Switching (MPLS). A PDN-GW 305 may further encapsulate this with an outer IP, User Datagram Protocol (UDP), and general packet radio service Tunneling Protocol (GTP). An S-GW 304 may also transmit the Ethernet data by outer IP, UDP, GTP, inner IP, GRE, and MPLS. An eNodeB 303 may remove the outer IP, UDP, and GTP. User equipment 301 may remove the inner IP, GRE, and MPLS to retrieve the Ethernet data.
In communication networks it is generally desirable to prevent service outages and/or loss of network traffic. By way of example, such service outages and/or loss of network traffic may occur when a network element fails, loses power, is taken offline, is rebooted, a communication link to the network element breaks, etc. In order to help prevent such service outages and/or loss of network traffic, the communication networks may utilize inter-chassis redundancy (ICR). ICR is a high availability (HA) solution that increases the availability of network elements, and may optionally be used to provide geographical redundancy. ICR is commonly implemented through a mated pair of an active network element and a standby network element. The active network element handles current sessions using session state that is built up over runtime. The session data is synchronized or replicated from the active network element to the standby network element. The standby network element begins to handle the sessions when an ICR switchover event occurs.
ICR is commonly used in LTE networks to help to provide resiliency. However, when Layer 2 data is transmitted through the LTE network, the conventional ICR system may not provide sufficient protection against service outages and/or loss of network traffic.